Sulfur deposition in downhole tubular and wellhead equipment associated with sour gas wells is usually troublesome to sour gas producers. Elemental sulfur, H.sub.2 S, and polysulfides are the principal sources of these unwanted sulfur deposits.
Dialkyl disulfides, alkyl disulfides and polysulfides, and particularly dimethyl disulfide (DMDS), CH.sub.3 SSCH.sub.3, are effective sulfur-dissolving agents or solvents for cleaning sulfur deposits. The relatively low flammability and vapor pressure of DMDS make it very attractive as a sulfur-dissolving solvent in sour gas wells. Further, DMDS can be efficiently regenerated through chemical wash. In the present application and aforementioned cross-referenced patent application, DMDS is regenerated in a multistage continuous countercurrent flow extractor.
Many processes in the prior art are known for the extraction of dissolved sulfur from solvents. For example, in U.S. Pat. Nos. 3,474,028, 3,489,677, 3,617,529, 3,748,827, 4,018,572, and 4,230,184, the use of alkali metal and ammonium hydrosulfides and sulfides to remove dissolved sulfur from mineral oils are disclosed. The publication of Dowling, Lesage, and Hyne for Regeneration of Loaded Dimethyl Disulfide Based Sulfur Solvents, Alberta Sulfur Research Limited Quarterly Bulletin, Vol. XXI, Nos. 3 & 4, pp. 30-52, October 1984-March 1985, discloses the regeneration of dimethyl disulfide by stripping sulfur from dimethyl polysulfide (DMPS) in a batch operation with alkali metal and ammonium hydrosulfides and sulfides, preferably sodium sulfide. None of the above prior art references discloses or suggests however the instant continuous multistage countercurrent flow extraction apparatus for removing sulfur from organic polysulfides.
The extractor apparatus of the present invention comprises a vertical multistage column extractor or reactor containing a distributor means at each end thereof, each of the stages comprising a packing section; a pair of redistributor plates with an agitator therebetween, each of the above recited components being spaced from each other, as well as from the packing section of an adjacent stage. A final packing section is provided adjacent that distributor means devoid of one adjacent thereto such that a packing section is disposed interiorly each distributor means.
The arrangement of components within the extractor and within each stage thereof insures efficient countercurrent flow of the two immiscible liquids, i.e., the stripping or extraction solution, typically aqueous Na.sub.2 S, and the sulfur-laden liquid organic phase (DMPS), such that high interfacial area contact is constantly maintained between the liquids .